Incidentally the ECG shows a Wenkebach AV block in the bottom strip lead 2.

I thought it was RVH. (do considered RBBB) but since lead V 2 showed tall R , I was more than sure RVH was likely . Many voted for RBBB. .Some others said RBBB can never occur in monophasic form.I said it’s possible.

Some body challenged me without Echo Imaging a monophasic RBBB can never be differentiated from RVH. After a mini argument I reluctantly agreed.Yes, it seemed there is no way to differentiate the two.

What do you think ?

Curious to know the Echo finding in the above patient ? Yes , your guess was right /wrong. There was no RVH.He had normal Echocardiogram.

How to diagnose RVH in RBBB ?

Look at the r’ wave if its taller than initial r by more than 5mm suggest RVH (Not absolute evidence though)

Look for other evidence like Right axis , RV strain etc.

How to diagnose RBBB in RVH ?

Sorry.I don’t know the exact answer.It could be masked within Qrs complex of RVH.RVH could convert biphasic RBBB into monophasic RBBB.

Some more about this RVH/RBBB duo

The term incomplete RBBB is liberally used with minor rsr’ pattern.It is not advisable to do so.

RBBB is classically multiphasic (To be precise RBBB can be complete to incomplete rsr’ with various combinations of small r and big s big R or big S).

But more than the morphology of Qrs in V1 the S wave in lead V 6 or Lead 1 could be Important.It should be delayed slurred.

QRS width has no great use to diagnose RBBB as it can be narrow or wide.

Final message

To diagnose monophasic RBBB( in V1 ) by itself requires some guts.However ,the entity do exist.

Finally , please recall there is a traditional list for tall R in V1 other than RVH.

Wrong lead placement

RBBB

Some cardiomyopathy(RV myopathy)

Systemic Duchenne’s muscular dystrophy

Pre-excitation

Posterior MI

Normal variant*

*Why should normal guys grow a tall R in V1 , it mystifies ! but true.

Annexure : Further questions in RBBB

1.How does AV bundle penetrate to become bundle of HIS and branches ?

Note AV node is fully Intra atrial structure , while part of His bundle is atrial , after crossing the membranous septum second part lies within the ventricle at the crest of muscular septum .Then the bundle of His goes for the famous division. Left fans out tow streams, while right descends on right side of IVS. Note : Applied anatomy 1.Its this small portion of HIS we are trying to physiologically pace the ventricle 2.In proximal LAD lesions both RBBB and LBBB is common still LBBB can’t be used to localise but RBBB can be.Guess why ? Read the next question and find the answer..

Is it true RBBB or Right bundle delay ? Students should know there need not be conduction system pathology to cause RBBB. Simple delayed conduction in RVOT can cause a RBBB. (The concept of central RBBB vs Peripheral RBBB) This is what happens in ASD.

In fact , true pathological damage due to right bundle branch due to necrosis, Ischemia, Infiltration is much rarer than pathological LBBB.

4. What are the structural , histological difference between right and left bundle branches that has electrophysiological Importance ?

Wait . . . I am trying to collect info for this .Meanwhile ,Why don’t one of the energetic young fellows in cardiology find the answer and post here !